maintain my own whitelist

You can certainly maintain your own whitelist by modifying the file .spamassassin/user_prefs in your home directory.  If this is too technical for you then we can set up a simpler system for you.  Go to the control panel and select user features.  Select "Whitelist" from the features and enter your whitelist there.   You can include wildcards (e.g. "*@example.com") in the address.  Let us know at support@Vex.Net and we will fix up your Spamassassin configuration file to use that list.  Remember, you must have us modify your configuration before the whitelist that you enter is active but once we have you can update your list at any time.